How to find next UserTask across two sub-processes

I built a process with two sub-processes A and B. There is a ErrorEndEvent EE1 in A, and with a ErrorBoundaryEvent EB1 in pairs. The EB1 connect to sub-process B. I want to find the first UesrTask in B with path EE1 -> EB1 -> Sub-process B -> (UserTasks).

But the path is end with EE1, and no way is found to connect EB1. I don't know how to use error event signal to find EB1 through EE1's errorCode. And also have no idea to find the next UserTask across sub-processes A and B.

Many thanks for your help. I have got the "errorCode" value in EE1 in sub-process A. I traversed all activities in ROOT level trying to get BE1(ErrorBoudanryEvent) activityImpl with the same "errorCode". But I failed on it. I could get all ErrorBoundaryEvent activities through "type" property. But I couldn't make a decision which one is BE1. There is no property called "errorCode" in activityImpl. Or no ErrorBoundaryEventActivityBehavior like ErrorEndEventBehavior having getErrorCode method. I only got BoundaryEventActivityBehavior via activityImpl.getActivityBehavior() method, but there is no property or method for me to subscribe "errorCode". Seem there is no extend class inherited from BoundaryEventActivityBehavior to handle ErrorBoundaryEvent.